when you purchase the soda sticker it is a flat rate, you will not see any charges on your account for soda or soda gratuity.
I thought that the fountain soda was just fine, as did my husband and teenage son who is pretty picky about his soda.
I would imagine that the gratuity is built into the cost of the soda sticker.
FYI the soda sticker does not cover virgin cocktails or bottled water.